The following acronyms are used in this application:
APammonium perchlorateANammonium nitrateADNammonium dinitramideBAMO/AMMObis-azidomethyloxetane/azidomethyl-methoxetane copolymerBAMO/NMMObis-azidomethyloxetane/nitramethyl-methoxetane copolymerGAPglycidyl azide polymerHANhydroxylammonium nitrateHAPhydroxylammonium perchlorateHNFhydrazinium nitroformateHTPBhydroxyl-terminated polybutadieneNPnitronium perchloratePBANpolybutadiene acrylonitrilePoly NMMOPolynitramethylmethoxetane
Solid propulsion systems could provide very high specific impulse by utilizing high performance oxidizers such as ADN, HAP, HAN, HNF, NP and the like. Many of these oxidizers offer significant gains on performance, reduced or low toxicity and have desirable exhaust signature characteristics, when compared to propulsion systems using traditional solid oxidizers. However, many of these oxidizers suffer from varying degrees and forms of instability, such as photo sensitivity, shock, friction and impact sensitivity, decomposition in the presence of moisture, sensitivity to pH and incompatibility (such as hypergolic reaction) to other propellant materials. A typical example of incompatibility is reaction between HNF and curing agents used in solid propellant binder systems such as HTPB and GAP. Many difficulties have been encountered incorporating the oxidizers into propellant systems, and solutions to particular storage and stability problems often result in compromising the theoretical performance potential. For example, current techniques to synthesize HNF still produce particles with length to diameter ratios of 2:1 to 3:1 with significant variation from the mean. This seriously impacts formulation rheology and can prevent achievement of optimum solids loading, as well as aggravating friction sensitivity during mixing and casting operations.
Storing the oxidizer separately in the motor offers the ability to avoid compatibility issues between oxidizers and common solid propellant system components. Separate storage of solid and semi-solid oxidizers and expulsion systems have been proposed and demonstrated in the past. Some of the difficulties in these approaches include flow stability, concentration and distribution of oxidizer solids in carrier agents, pressurization and piping system requirements, specialized control valves and system integration.
Improvements or alternatives in solid propellant systems for rockets would be useful.